code: def _keys_(self):
      cls = type(self)
      member = "__keys_" + cls.__name__
      try:
          return getattr(cls, member)
      except AttributeError:
          slots = sorted(self._FIELDS)
          setattr(cls, member, slots)
          return slots
  
imports: from typing import Dict, Tuple, Type
  from ..serialization.serializables import Serializable, StringField
  from ..serialization.serializables.core import SerializableSerializer
  from ..utils import tokenize
label_desc: Use image node_id 2 for calling the Base obj's underlying member method code with example usage: obj._keys_() and returns: getattr, slots